1. Field of the Invention
The present invention relates to a keyboard apparatus of an electronic musical instrument, the keyboard apparatus having massive bodies which pivot in synchronization with key-depression.
2. Description of the Related Art
Conventionally, a keyboard apparatus of an electronic musical instrument is designed such that massive bodies pivot in synchronization with key-depression in order to provide its players with the feeling of key touch, more specifically, the feeling of mass and the feeling of stop similar to those offered by a keyboard mechanism of an acoustic piano.
A keyboard apparatus disclosed in Japanese Unexamined Patent Publication No. H9-198037 has an upper surface board provided on a rear part of a casing which accommodates the rear end (key fulcrum) of respective key main bodies. To the undersurface of the upper surface board, a stopper (upper limit stopper) is fixed. Bent portions (mass concentrated portions, free ends) of spindles (massive bodies) extend far behind the rear end of the key main bodies. At the time of key-depressions, the bent portions collide with the upper limit stopper. According to this structure, the depth of the keyboard apparatus has to be large. Furthermore, the stroke length of the free end increases with increase in the distance from a fulcrum of the spindle to the free end. Therefore, unless the angle at which the massive bodies pivot is reduced, the height of the keyboard apparatus is made high.
In Japanese Unexamined Patent Publication No. H4-142595 and Japanese Examined Patent Publication No. H2-019468, keyboard apparatuses in which the above-described massive bodies are placed below the keys are disclosed. In these cases, the depth of the keyboard apparatuses is the same as that of a keyboard apparatus having no massive bodies.
In the keyboard apparatus disclosed in Japanese Unexamined Patent Publication No. H4-142595, hammer arms (massive bodies) are provided on the undersurface of a keyboard chassis (frame) situated in front of axes (key fulcrums). However, the height of the keyboard apparatus is obtained by adding a sidewall of a key, a stroke length of a key, a clearance between a key and the keyboard chassis, a thickness of the keyboard chassis, a thickness of a stopper member (upper limit stopper), a stroke length of a hammer arm, a height of a hammer arm, a thickness of a damping member (lower limit stopper), and the like. By providing the hammer arms, therefore, a problem that the shape of the keyboard apparatus becomes higher to make the electronic musical instrument bulky arises.
In the keyboard apparatus disclosed in Japanese Examined Patent Publication No. H2-019468, axes (pivot fulcrums) of respective arms (massive bodies) are fit into concave portions provided on right and left side walls of the respective keys, with cushion members (upper limit stoppers) of the arms being provided on a ceiling surface located inside the respective keys. When a key is depressed, the arm gets into the inside sandwiched between the right and left side walls of the key. Therefore, because unused space which is situated inside the right and left side walls of the respective keys is utilized, the height of the keyboard apparatus can be reduced. However, because the cushion member is placed inside the respective keys, a problem that a shock caused by collision of the arm with the cushion member is perceived by a player with his finger through a key arises. In addition, because the cushion member has to be provided for the individual keys, a problem that the conventional apparatus decreases the efficiency of assembly to require more assembly cost, compared with a case where all the keys share a cushion member.